1. Field of the Invention
The present invention relates to air-drying fatty acid-modified acrylic resins. More specifically, the acrylic resins comprise copolymers of glycidyl (meth) acrylates and other appropriate ethylenically unsaturated monomers which are reacted with fatty acids and subsequently reacted with isocyanates. The invention further relates to the combination of the acrylic resins with a novel catalyst system comprising a primary drier and an activator for said drier comprising a coordination complex of titanium.
Generally, the use of fatty acid-modified acrylic resins as film-formers is known in the art. However, films formed therefrom have been known to have shortcomings, pertinent among which is poor caustic resistance. Hence, there is a need for preparing fatty acid-modified acrylic resins which have improved caustic resistance properties as well as other desirable composition, coating and film properties.
The cure of compositions containing these resins is aided by catalysts or driers which are typically hydrocarbon soluble salts of selected metals. Illustratively, metal salts such as octoates, naphthanates, linoleates, neodecanoates have been used as catalysts or primary driers. Auxiliary driers which are believed to have an activating effect on the primary driers are also employed. Hence, they are alternately referred to as activators. Typical examples of the activators are calcium, barium, and zinc salts. Over recent years, it has become common practice to add selected compounds to surface coatings to increase the efficiency of the metallic driers. These compounds have in common the ability to form coordination complexes with transition metal ions. Typical of the complexing agents is 1:10 phenanthroline.
The present invention provides a new drier activator comprising a coordination complex of titanium. U.S. patent application Ser. No. 534,948, filed even-date, relates to the coordination complex of titanium as a drier activator.
2. Summary of the Invention
In accordance with the foregoing, the present invention encompasses an air-drying fatty acid-modified vinyl polymerized resin comprising:
(i) a copolymer of ethylenically unsaturated monomers, at least one of which contains an epoxy group, which has been esterified with PA1 (ii) an air-drying fatty acid with the resultant formation of hydroxyl group(s) which are reacted with a monoisocyanate.
The present invention further encompasses a curable composition comprising the afore-stated vinyl polymerized resin in combination with a drier catalyst system, comprising a drier which is typically a metal salt and a drier activator which is a coordination complex of titanium.
A presently preferred embodiment of the catalyst system comprises the coordination complex of titanium, which is titanium II diisopropyldiacetoacetonate (hereinafter Ti II AcAc). In a particularly preferred embodiment of the catalyst system, the Ti II AcAc is used with cobalt salt as the primary drier (hereinafter the term "cobalt" or "Co" denotes cobalt salt). Also, the present invention encompasses a method of air drying curable compositions containing the instant acrylic resin with art-known catalyst systems or with the instant catalyst system. Articles of matter coated with said compositions are also encompassed.
It has been found that coating compositions comprising the resins of this invention are stable, and form air-dried films which have excellent properties. The films have excellent color, gloss, water resistance, solvent resistance, exterior durability, caustic resistance and other desirable properties. It has also been found that the coating compositions comprising the afore-stated drier catalyst system are stable and cure in a remarkably short period of time to tack-free and through-cure state.